The Digital Television Revolution

The 2012 London Olympics actually brought home to me just what a enormous technological leap in electronic media has occurred during the past couple of years. There’s been significant progress in digital compression and transmission.

This year, along with high definition broadcast, which made its appearance from the 2008 Beijing games, 3D television was also added to the lineup, offering more channels and options. With analogue television broadcast almost becoming extinct, digital televisions promise of delivering more for less is becoming a reality.

Before the digital switchover, analogue television was source hungry concerning the amount of bandwidth necessary to carry a single station.

This limited the amount of channels that might be transmitted, since there’s a limited amount of spectrum that has to be shared with other services like radio and two way communications.

Digitial television

What the electronic standards of ATSC (North America) and DVB (Rest of the World) provided was the ability to reuse the present analogue spectrum better. This meant a normal 8 MHz carrier used for analogue broadcast could be converted into DVB-T (Digital Video – Terrestrial) which makes it feasible to carry 9 standard definition channels or 3 HD channels and one SD channel for the identical amount of bandwidth.

It would have required in excess of 70 MHz of frequency spectrum to accomplish this with the older analogue standard. Besides squeezing more channels into less space, digital tv is significantly clearer and does not suffer from ghosting or other artifacts that troubled analogue systems.

Becoming electronic also allows other features like enhanced digital audio, digital program guide and subtitle support to be included.

Televisions are offered with the digital decoder incorporated and older televisions may use another set top box. As technology advances, we’ll also see improvements in the compression methods used, which means more content for electronic media, already that has enabled 3D broadcasts for some events like the Olympics.

The Future

Finally as fibre to the home is deployed globally, the IP enabled set top box will replace the DVB standard, because the IP set top box has a distinct advantage over digital broadcast technologies, especially multicast join requests. Unlike DVB-T or DVB-S, IP multicast enables the recipient to send a join message to the system for the desired channel then when the petition is successful the broadcast is sent to the recipient, only the bandwidth to the requested channel is utilized. Together with the DVB standard, all available channels are being broadcast simultaneously, and the station count is restricted by the finite quantity of channel bandwidth whatever the compression techniques used.

But, unlike DVB, IP set top boxes need to be worried about latency and QOS, because there’s traffic contention with both residential broadband and IP Telephony. A badly implemented IPTV deployment can act like analogue television in an over subscribed service provider network, unless the right traffic management is in place.

High Definition

Today HD is seen as premium content by the majority of operators and is billed at a higher rate than SD (Standard Definition). But over time this will change as people upgrade their televisions to HD versions. In 720p broadcast, the image is created of 720 horizontal scan lines and a vertical resolution of 1280 pixels, which has the benefit that one framework represents a whole image.

HDTV logo

In 1080i broadcast, the image is created from two 540 horizontal scanning images that when combined create 1080 lines. Most modern televisions support playback of 1080p, which is more desirable than 1080i particularly in fast moving sequences where motion blur could be gotten. But on modern televisions that the difference is barely discernible.

Originally the people uptake of HD was slow, the recipients were expensive and the accessible content was restricted. HD television has been an evolution as opposed to a radical change for most of us and this is also true of digital television generally. However, it’s unfortunate that technology will not help to enhance the content.